What's the objective of this collecting?

I heard a talk last year from the Canadian singer/ethnomusicologist Brenna MacCrimmon (her thing is Western Turkey, Thrace and the Balkans). She said it was SOP for ethnomusicologists arriving in a new area to first hit the local market and buy up all the kitchen cassettes they could. When I first went to Istanbul I'd often see people selling Kurdish cassettes (only marginally legal and sometimes well over the line with the more political stuff) from small barrows, so they could beat it quickly when the cops started taking an interest.

So for something like Kurdish political song, I can see the point. But the sheer volume of low-budget Anglo-American singer-guitarist music must make undirected accumulation a bit like stamp collecting - you'll never get them all.